46 
is foreshortened, and the nervous system is highly 
concentrated. In a few cases only, such as in the 
crayfish, do the 
young ones re- 
semble the per- 
fect animal 
when they quit 
the egg. More 
frequently, the 
newly hatched 
Crustacea ex- 
hibit a larval 
form called a 
Zoea, which 
has only a few 
pairs of limbs, and does not possess all the thoracic 
segments, but is furnished with peculiar spines, and 
is of almost microscopic dimensions. 
Suborder I, 
The carapace completely covers the head and 
thorax in one piece. 3 of the 8 pairs of thoracic 
legs are converted into foot-jaws, leaving 10 legs 
fitted for walking. There are two sharply defined 
sections, in one of which the abdomen is reduced 
to a mere plate, while in the other it is well deve- 
loped, and nearly as large as the rest of the body. 
Tribe I. Macrura. 
Fig. c. Astacus fluviatils, the Cray-fish, may 
be taken as the typical illustration of the section in 
which the abdomen is well developed. The accom- 
pany ing figure represents the undersurface. The last 
pair of abdominal legs is expended into Plates, and 
forms a kind of eras 
tail-fin (2). The 
first pair of walk- 
ing legs is armed 
with large pin- 
cers, and the se- 
cond and_ third 
pairs have also 
pincer-like termi- 
nations, which is 
a character of the 
family Astaccde, 
to which the cray- 
fish belongs. This 
wellknownanimal \ 
is of a dark brown 
colour, and is 
foundeverywhere 
in Europe on 
riversandstreams 
under stones and 
in holes on the 
banks, and feeds 
on animal mat- 
ters. The calca- 
reous masses called ‘“‘crabs-eyes”’ are outgrowths from 
the surface of the stomach. The redness caused 
by cooking is due to the destruction of the brownish 
colouring matter of the shell, which developes a 
second layer of red colouring matter. 
Fig. d. Homarus vuleari zs, the Lobster, is 
very like the Crayfish, but is much larger, and lives 

Decapoda. 


“St thy eZ 
| Suh a= ale 
Female Crayfish (lower surface), 
a) Inner antenne. b) Outer antenne. 
d) Auditory organs. e) Foot-jaws. 
legs. g) Fifth pair of legs, 
dages. j) Vent. 
c) Eyes. 
f) First pair of 
h) Abdominal appen- 
i) Outer scale of tail-fin. 
in the European seas; a nearly allied species is found | 
North America. ie Lobster is 
into which it creeps during the 
Its importance as an article of food may be 
on the coast of 
caught in baskets, 
night. 


estimated by the fact that about 13 millions are annu- 
ally consumed in Europe and in North America. 
Fig. e. Palinurus vulgaris, the Spiny Lobster, 
represents the family Zovzcata, in which the five 
pairs of legs do not end in pincers. The outer an- 
tenne are longer than the body, and their basal 
joints are thick and spiny. It is common in the 
European seas, and sometimes attains a weight of 
six pounds. Its flesh is more esteemed on the coasts 
of the Mediterranean than in England. 
In the family Cavzdintde, which includes the 
Shrimps and Prawns, the cephalothoracic shield is 
generally produced 
into a large beak, 
and the first 2 or 
3 pairs of legs fre- 
quently end in small 
pincers. Enormous 
numbers of the com- 
mon shrimp (Craz- 
gon vulgaris) are 
swept up with nets 
on the sand in shal- 
low water, as well 
as Prawns (Falemon serratus) which are larger, and 
armed with a strong frontal spine. 
In the Hermit Crabs (Pagurid@) the abdomen 
is extremely soft, and therefore the animals shelter 
themselves in shells, which they trail about after them. 
The first pair of legs ends in two pincers of unequal 
size. One of the commonest species is Pagurus 
Bernhardus (fig. f), which shelters itself in whelk- 
shells. 

Prawn, 
Tribe II. Brachyura. 
In the Crabs the abdomen is short, and is 
curved under the hollowed undersurface of the shell, 
so that the body is often broader than long. The 
first pair of legs is provided with claws. Some crabs 
are able to live on land and climb trees, though most 
of them live in the sea. They run quickly, but 
always sideways. 
Fig. g. Gecarcinus ruricola, the Land Crab, 
may be taken as a representative of the crabs with 
a square shell. It is found in the West-Indian Islands, 
where it lives in holes some miles from the sea. 
It is about eight inches broad. 
Other genera of this section are marine. The 
species of /zxnotheres are found between the valves 
of different bivalve shells, especially Prxza. 
Fig. h. Cancer pagurus, the Edible Crab, be- 
longs to another group, with a broad shell, rounded 
in front. It sometimes attains a breadth of fifteen 
inches and a weight of six pounds. 
Fig. i. Maza sguinado, the Spider Crab, has 
a triangular pointed carapace, and is covered with 
spines and shaggy hair. It is very common in the 
European seas. 
Suborder H. Schizopoda. 
In this group, the three first pairs of legs are 
not true footjaws, but are used for walking, and like 
the other legs, are biramous and bristly. The ab- 
dominal legs are generally rudimentary in the female, 
but are used for grasping organs in the male. The 
few species belonging to this group are all inhabitants 
of the open sea, and some, as the genus J/yszs, are 
parasitic on whales in all stages of their existence. 
| They resemble shrimps in form. 
